Use your Windows password for your screen saver password
You can help make your computer more secure by creating a screen saver password, which locks your computer when the screen saver is on. The screen saver password is the same password that you use when logging on to Windows.
Open Screen Saver Settings by clicking the Start button , clicking Control Panel, clicking Appearance and Personalization, clicking Personalization, and then clicking Screen Saver.
Select the On resume, require logon check box, set a time after which to start the screen saver, and then click Apply. (Choose a wait time that's not long enough for an unauthorized person to use your computer, but not so short that if you are idle for a moment, the screen saver locks your computer.)
If Fast User Switching is turned on, select the On resume, display logon screen check box.